1. 1 Mariyan Bogomilov CERN,(Switzerland) University of Sofia and INRNE, (Bulgaria) GAS@BSGAS@BS, Kiten, Bulgaria GAS@BS THE HARP EXPERIMENT THE HARP EXPERIMENT On behalf of the HARP Collaboration 13-20 June 2005

2. 2 Motivation for HAdRon Production experiment neutrino factories Pion/kaon yield for the design of the proton driver and target systems of neutrino factories

3. 3 Maximizing  + (  - ) production yield as a function of Target material Proton energy Geometry Collection efficiency Poor experimental knowledge : Few material tested Large errors (small acceptance) Different simulations show large discrepancies for  production distribution, both in shape and normalization. factory design factory design  need to measure  yield and  + /  - ratio better than 5%  need differential distributions (P L,P T )

4. 4 Motivation for HAdRon Production experiment neutrino factories Pion/kaon yield for the design of the proton driver and target systems of neutrino factories MiniBooNE K2K Input for prediction of neutrino fluxes for the MiniBooNE and K2K experiments

5. 5 Analysis for K2K: motivations MC only

6. 6 K2K interests pions producing neutrinos in the oscillation peak K2Kinterest K2K far/near ratio Beam MC Beam MC, confirmed by Pion Monitor To be measured by HARP 0.5 1.0 1.5 2.0 2.5 0 E  (GeV) oscillationpeak One of the largest K2K systematic errors on the neutrino oscillation parameters comes from the uncertainty on the far/near ratio beam 250km

7. 7 Motivation for HAdRon Production experiment neutrino factories Pion/kaon yield for the design of the proton driver and target systems of neutrino factories Input for prediction of neutrino fluxes for the MiniBooNE and K2K experiments Input for precise calculation of the atmospheric neutrino flux (from yields of secondary p,K)

8. 8 Atmospheric flux Primary flux is now considered to be known better than 10% Most of uncertainty comes from the lack of data to construct and calibrate a reliable hadron interaction model Model-dependent extrapolations from the limited set of data lead to about 30% uncertainty in atmospheric fluxes Need measurements on cryogenic targets (N 2, 0 2 ) covering the full kinetic range in a single experiment

9. 9 Motivation for HAdRon Production experiment neutrino factories Pion/kaon yield for the design of the proton driver and target systems of neutrino factories Input for prediction of neutrino fluxes for the MiniBooNE and K2K experiments Input for precise calculation of the atmospheric neutrino flux (from yields of secondary , K) Input for Monte Carlo generators (GEANT4, e.g. for LHC or space applications)

10. 10 HARP physics goals Precise (~2-3% error) measurement of differential cross-section for secondary hadrons by incident p and  ± with: Beam momentum from 1.5 to 15 GeV/c Large range of target materials, from Hydrogen to Lead Thin and thick targets, solid, liquid and cryogenic K2K and MiniBooNE replica targets ► Acceptance over the full solid angle ► Final state particle identifications

11. 11 The HARP Collaboration 124 physicists24 institutes BariBari University, CERNCERN, DubnaDubna JINR, DortmundDortmund University, FerraraFerrara University, GeneveGeneve University, P.N. LebedevP.N. Lebedev Physical Institute, LegnaroLegnaro /INFN, Louvain-la-NeuveLouvain-la-Neuve UCL, MilanoMilano University/INFN, MoscowMoscow INR, NapoliNapoli University/INFN, OxfordOxford University, PadovaPadova University/INFN, ProtvinoProtvino IHEP, Protvino, ParisParis VI-VII University, RALRAL, Roma IRoma I University/INFN Roma TreRoma Tre University/INFN, SheffieldSheffield University, Sofia Sofia Academy of Sciences, Sofia Sofia University, Trieste Trieste University/INFN, ValenciaValencia University

12. 12 Data taking summary SOLID: CRYOGENIC: EXP: HARP took data at the CERN PS T9 beam-line for 2 years Total: 420 M events, ~300 settings Element Thickness, Beam momentum K2K: AlMiniBoone: BeLSND: H 2 O 5% 50% 100% Replica 5% 50% 100% Replica 10% 100% +12.9 GeV/c+8.9 GeV/c+1.5 GeV/c

13. 13 Detector layout Large Angle spectrometer Forward spectrometer

14. 14 Beam detectors TOF-A CKOV-A CKOV-B TOF-B 21.4 m T9 beam MWPCs Two beam Cherenkov:  /K above 12 GeV ~100% e-  tagging efficiency MWPC: incident beam direction with σ<100μm,  =96% Beam TOF:  /K/p at low energy T0 with σ~70ps Proton selection purity > 98.7% 12.9 GeV/c  K p d Corrected TOF (ps) 3 GeV

15. 15 Large angle spectrometer: TPC dE/dx P (GeV/c)  p  P T /P T P T (GeV/c)  p t = abs(  1 +  2 ) p t √2(  tot )

16. 16 Large angle spectrometer: RPC Two groups: barrel and forward plane 46 chambers; 2 layers; 368 pads Intrinsic barrel time resolution: ~220 ps Combined resolution (RPC+TPC+BEAM) ~ 330 ps Beta=v/c P (GeV/c)  p

17. 17 Forward acceptance A particle is accepted if it reaches the second module of the drift chambers P > 1 GeV K2K interest dipole magnet NDC1 NDC2 B x z NDC5 beam target Top view 1 2 NDC3 NDC4 Plane segment 3

18. 18 Forward tracking dipole magnet NDC1 NDC2 B x z NDC5 beam target Top view 1 2 NDC3 NDC4 Plane segment 3 3 track types depending upstream information 1.Track-Track 2.Track-Plane segment 3.Track-Target/vertex recover efficiency and avoid dependencies on track density in 1st NDC module (model dependence) Calculate efficiency separating downstream system first: Downstream Upstream

19. 19 Tracking efficiency P, GeV/c  x, rad  y, rad

20. 20 Tracking efficiency P, GeV/c  x, rad  y, rad

21. 21 Reconstruction efficiency P, GeV/c  x, rad  y, rad

22. 22 e+e+ ++ p number of photoelectrons  inefficiency e+e+ h+h+ TOF CHERENKOV CALORIMETER 3 GeV/c beam particles ++ p 0 1 2 3 4 5 6 7 8 9 10  p P (GeV)  e  k TOF CHERENKOV TOF CHERENKOV CALORIMETER TOF CHERENKOV CAL Forward spectrometer: PID

23. 23 Analysis for K2K In K2K: E : 0 ~ 5 GeV P  < 10 GeV/c  < 300 mrad Most important region oscillation max: E ~ 0.6 GeV 1 GeV/c < P  < 2 GeV/c 1 GeV/c < P  < 2 GeV/c  < 250 mrad  < 250 mrad E PP  P  vs  Study interactions of 12.9 GeV protons on Al with the HARP Forward Spectrometer Oscillation max

24. 24 Combined PID probability Bayes theorem: TOFcherenkov By MC:  electrons have a peak in low energy;  the particle is rejected if p 15; where j = p,  By data:  Kaons are estimated  And subtracted

25. 25 where: M – unfolding momentum matrix - between true and measured momentum J – Jacobian of transformation between measured and ‘true’  - inverse tracking efficiency - inverse geometrical acceptance Raw yield for K2K thin target K2K replica target 5% Al target 200% Al target

26. 26 Then:  Corrections for absorption (not reaching downstream detector) ~ 10- 20%  Correction for secondary interactions( in the target and not coming from vertex) ~5%  Empty target subtraction  Subtraction of electrons and kaons  PID criteria by where  ij is the fraction of observed j to be true i True pion and proton yields

27. 27 Cross-section calculation Pion cross-sectionPion yield A - atomic number N 0 - Avogadro number  - density Z – target thickness N pot – number of protons on target

28. 28  7 mln. triggers  3.054 mln. incoming protons  170 000 secondary tracks  + cross-section (graphics) + data … Stanford-Wang fit PRELIMINARY

29. 29  + cross-section (table) PRELIMINARY

30. 30Conclusions The HARP Experiment has collected data for hadron production measurements with a wide range of beam energies and targets Detector, PID, tracking efficiency well understood and robust First cross-section data are available: thin (5% ) K2K target, using forward region of the detector In the near future HARP will provide many important results, not only for physics !

31. 31 MiniBooNE beam phase space Momentum and Angular distribution of pions decaying to a neutrino that passes through the MB detector. Acceptance of HARP forward detector 8.9 GeV beam interactions on MiniBooNE replica Be target cooling fins

32. 32  yield for the MiniBooNE thin target Iterative PID algorithm on Be 5% target data to extract raw pion yields. PRELIMINARY